I. Field of the Invention
Our invention relates generally to devices for sampling and testing particulate matter, including materials such as wood flakes and the like. More particularly, this invention relates to product monitoring devices characterized by remote, rotatable heads disposed within a product conveying chute that may be moved towards or away from the direction of particulate flow to captivate a sample. Known prior art relative to our invention is seen in Class 73, Subclasses 863.51, 863. 52, and 863.56.
II. Description of the Prior Art
A variety of contemporary wood products such as oriented strand boards and laminates are formulated from wood flakes and particles. These flakes are manufactured on site from billets or tree length wood. Raw wood chips are shipped in bulk to various manufacturing installations. The large, fungible mass of chips arriving at the manufacturing facility is of inconsistent density and moisture content. For quality control purposes a uniform mixture is desirable. One or more drying and mixing stages are commonplace.
A typical manufacturing process may pneumatically transport raw wood flakes from the critical drying stage to various downstream process stages. Between the process stages, flakes are sucked through a large pipe. It has been previously recognized by those skilled in the art that product quality may be better controlled if consistency in moisture content is achieved. The ability to sample the wood flakes immediately behind the drying process and check the moisture content allows the drying operations to be more closely controlled. Moisture readings of critical samples derived downstream may be employed to derive critical dryer control signals used to modify manufacturing parameters upstream. These readings can be used, for example, to speed up or slow down the flow of wood flakes through the drier. Where for example, oriented strand board is being manufactured; the flake moisture content must be tightly regulated. If the incoming flakes are over-dried, too much glue will be used. If the flakes are too moist, too little glue will be used. This can seriously affect the delamination of the finished product.
Prior art sampling devices collected wood flakes travelling within a pipe or conduit with a fixed, inlet end. Often design limitations inherent in prior art fixed sampling ends made it difficult for the monitored product to be sampled properly. The particulate mass flowing through a typical wood flake delivery pipe, for example, comprises a variety of wood particles of different sizes and moisture.
The wood drying in these inline processes has been largely uncontrollable because moisture reading of the end products was not obtainable for several minutes behind the drying operation.
A negative pressure blow pipe system is used for conveying the wood particles through the rotary drum drying operation in the process and the ability to sample the dried flakes immediately behind the dryer is a large step in better controlling the drying operation.
Because the typical granular mixture involves so many wood chips of different sizes and shapes, it has proven difficult to obtain a statistically representative sample that can be properly analyzed for process control. Usually fixed sample tubes obtain a more representative sample if they are mounted close to the pipe inlet. However, it is often cumbersome and inconvenient to mechanically mount the complex sampling apparatus immediately proximate an inlet. It is much more practicable to mount the sampling apparatus midstream, in an area that is easily and safely accessible to workman and equipment.
U.S. Pat. Nos.3,595,087 and 4,574,645 are the closest prior art references known to us. These patents show sampling mechanisms secured to transfer conduits. The samplers comprise rotatable hoods positioned within the flow path. Samples are captured, measured, and then discarded. The hoods may be rotated between a first operative position disposed directly within the flow path for capturing samples, and a second operative position disposed 180 degrees in the opposite direction. However, said devices do not perform the moisture determination; samples must be manually removed for testing at a remote location. Furthermore, samples are not automatically returned to the airstream after testing. While these systems are improvements over other more cumbersome designs, they tend to be slow, and corrective information needed for feedback to the remote drier cannot be derived and monitored in real time.
This invention provides a real time sampling and sensing system for monitoring characteristics (i.e., moisture content) of particulates (i.e., wood flakes.) The system comprises a sensor having a rotatable head thrust within the flow path of the particulate-laden airstream. When the rotary head is turned to face the flow of wood material, a sample is captured, and stored temporarily within a lower sensing chamber. The rotary head may then be returned to the downstream-facing position. Immediately afterwards the captivated sample may be xe2x80x9csensedxe2x80x9d to determine moisture content,
The wood flakes captivated within the lower part of the sensing chamber are held against a glass port, and an adjacent moisture meter reads the moisture. Afterwards, the valve in the lower section of the device is opened. Since the conveying system is operating under negative pressure (less than atmospheric) the sample is swept back into the material flow by the inrush of air.
The electrical information can be relayed to control circuitry to be processed into adequate control signals for feedback to the remote drier. In other words, corrective feedback signals may be generated virtually instantaneously with the capture of a particle sample, minimizing delays and errors.
Once the sample is discharged the damper shuts and the unit waits until an another capture signal is received. In response to such a signal, another sample is captured, read, and then returned to the conduit; in other words, the entire operation is repeated. Real time corrective parameters can thus be electronically produced concurrently with drier operation.
Thus a general object of our invention is to provide a dynamic sampling device for monitoring a stream of particulates.
More particularly, it is an object to provide a highly reliable monitoring system for sampling wood flakes traveling through a negative pressure pneumatic pipe.
Another basic object is to precisely control the moisture of wood flakes traveling through a manufacturing process.
Yet another object is to provide a dynamic sampling process of the character described that provides sufficient moisture feedback data downstream of a process to provide feedback and control signals used for adjusting and controlling an upstream process.
A related object is to automatically sample particulate materials as they are pneumatically transported, and to concurrently derive real time corrective parameters for feedback to the remote drier.
A basic object is to sample particulate matter, i.e., wood flakes, flowing through a negative pressure pipe with a minimum of product waste.
A related object of the present invention is to provide an improved moisture sample for wood flakes.
Also, it is an object to provide a moisture sampling and control system of character described that is ideally adapted to handle samples of particulate materials that vary widely in moisture content, size and shape.
Another important object is to provide a wood particle sampling system of the character described that returns samples, after deriving a reading, to the pneumatic pipe, thereby minimizing waste.
Yet another object is to provide a sampling device that may automatically and remotely be switched between product collecting and neutral positions.
These and other objects and advantages of the present invention, along with features of novelty appurtenant thereto, will appear or become apparent in the course of the following descriptive sections.